The present invention relates to a scroll compressor, and in particular, to an improvement in connection with a bearing and a balance weight that is advantageous in enhancing the reliability of and in reducing the vibration of a scroll compressor. Such a scroll compressor is used, though not exclusively, for refrigeration and air conditioning, and is preferably of a closed or hermetic type.
A conventional scroll compressor has a stationary and an orbiting scroll, each having a spiral wrap. These scrolls are meshed with respect to each other to define a plurality of compression chambers therebetween. An intake port is provided in the outer periphery of the stationary scroll, and a discharge port in the vicinity of the center of the same. Accordingly, as the orbiting scroll is making an orbiting movement, these compression chambers decrease their volumes gradually from the outer periphery of the stationary scroll towards the center thereof. As a result, a working gas, which has been sucked through the intake port and confined in these compression chambers, is gradually compressed to be discharged through the discharge port as high pressure gas.
Further, an electric motor for driving is provided close to the orbiting scroll, and a crankshaft, which is jointed to the rotor of this motor, is connected to the orbiting scroll. This crankshaft is rotatably supported by sliding bearings arranged respectively on both sides of the motor.
A scroll compressor structure as described above is shown, for instance, in Japanese Patent Laid-Open No. 59-28088. This known type of scroll compressor is of a hermetic type, wherein the bearing which is situated below the motor is mounted on a bottom plate which is separate from a compressor shell. Lubricating oil is forcibly supplied to each bearing from the outside of the compressor through this bottom plate.
Further, in a compressor of this type, since the orbiting scroll makes an orbiting movement along a fixed orbit, a large unbalance force results and is applied to the driving crankshaft. In view of this, the crankshaft is provided with a balance weight to cope with this unbalance force. Such a balance weight is shown, for example, in the above-mentioned publication as well as Japanese Patent Laid Open No. 62-271984.